Two “suspicious” letters containing white powere were discovered at different UN consulates today — a day after diplomatic missions in New York discovered similar letters, authorities said.

The latest letter was found at the United Kingdom’s UN consulate. Earlier today, a letter was found at Germany’s UN consulate. They’re both believed to be hoaxes.

But authorities still took the precaution of decontaminating areas of the German mission on the East Side, and also sent the powder out for testing at a local lab. The female consulate employee who opened the letter underwent decontamination and received medical attention. She later returned to work.

Consulate employee Jochen Wolter said that a mass e-mail was sent out to workers by the building’s administration at about 10 a.m. alerting them that an a suspicious letter had been received and that the 21st floor had been sealed. Soon afterward, NYPD officers, firefighters and FBI agents arrived at the scene.

FBI spokesman Richard Kolko said the German mission on United Nations Plaza received the letter this morning.

In addition to containing unidentified white powder, the letter also had an “an unusual and suspicious” message, Kolko said.

An NYPD spokesman said that the letter sent to the German Consulate is “likely related to the letters from yesterday and there will probably be more.”

The UN missions of Uzbekistan, Austria and France yesterday afternoon discovered those other letters, each of which contained a single-sentence, computer-generated note that said “Al Qaeda FBI in America,” but which did not make any demands or provide a motive for why the powder was sent.

All four letters bear a postmark from Dallas, Texas — albeit with different return addresses in that city — and they are believed to have been mailed from the same post office last Friday, sources said. The letters were mailed a day after the massacre of 13 people on the US Army base in Fort Hood, Texas, by Army psychiatrist Maj. Nidal Malik Hasan, who is Muslim.

Forty people underwent precautionary decontamination after the three letters were opened yesterday.

The city Health Department said the powder in those envelopes tested negative for anthrax, and was not otherwise harmful. It will take about a week to determine what the powder is made of.

“Anybody that thinks it’s a joke is making a very bad mistake. If we apprehend you, you’re going to face criminal charges. We’re doing an investigation, trying to figure out who it is. As a joke, it is not funny.”